Effects of bovine respiratory disease on the productivity of dairy heifers quantified by experts

The aim of the current study was to obtain expert data on the effects on productivity (EPs) associated with bovine respiratory disease (BRD) in dairy heifers. Expert knowledge on the EPs of BRD was elicited because a complete insight into these effects was not available from the literature. The experts' assessments of the EPs were quantified, applying the computerised ELI technique, by means of subjective probability density functions (PDFs). For each EP, the individual experts' PDFs were aggregated, hereby weighting the experts according to their expertise, to obtain a single weighted distribution per parameter. Results indicated that mortality following severe pneumonia in heifers < 3 months was assessed to be increased by nearly 20% (range 16-24%). Body weight of diseased heifers was estimated to be reduced by 10 kg (range 2-18 kg) at 3 months, up to 29 kg (range 23-36 kg) at 14 months. Furthermore, pneumonia was assessed to delay first calving age with half a month (range 0.1-0.9 months), and to reduce first lactation milk production by about 2% (150 kg, range 40-250 kg). BRD outbreaks in heifers ! 3 months were also estimated to reduce body weight at 14 months with approximately 30 kg (range 11-54 kg). The resulting EPs following BRD outbreaks were found to be less severe, and only occasionally as detrimental as the EPs associated with early pneumonia. It was concluded that the expert data obtained provide valuable information for economic decision-making in dairy practise. (C) 2002 Elsevier Science B.V. All rights reserved.